In recent years, fuel saving characteristics of vehicles are again regarded as important, as the global environmental issues are drawing more attention. As for the global environmental issues, measures need to be promptly taken against global warming. However, there is a limit on fuel reductions achieved by improvements in vehicles with conventional gasoline engines that emit greenhouse gases such as carbon dioxide, and rapid global warming cannot be effectively stopped.
To counter this problem, hybrid vehicles have been developed. A hybrid vehicle normally has a gasoline engine that uses fossil fuel as energy, and a motor that uses electricity as energy. For example, a hybrid vehicle uses a motor as the driving force at the time of low to medium speed driving, and uses a gasoline engine as the driving force at the time of high speed driving.
When running with a motor as the driving force, a hybrid vehicle does not emit exhaust gases at all. Accordingly, a hybrid vehicle has the effect to prevent further global warming, emitting no greenhouse gases. Also, since a motor uses electricity as energy, a motor can achieve higher energy usage efficiency, and realize more fuel saving than a gasoline engine. A fuel saving effect can be measured by measuring distances that can be traveled with the same amount of energy, or the amount of energy consumed to travel the same distance, and using them as indicators.
However, no matter how high the original fuel saving characteristics of the vehicle are, a driver's fuel consuming driving manner can degrade the high fuel saving characteristics of the vehicle. Therefore, there have been various conventional techniques for advising drivers to perform such driving operations as to save as much fuel as possible.
For example, according to a conventional technique, an in-vehicle display device that reports to the driver about how long the driver has performed eco-friendly driving has been suggested. If a travel distance converted into a unit amount with the use of fuel consumed at the present location is determined to be larger than a reference value, the driving of the vehicle is regarded as eco-friendly driving (fuel-saving driving friendly to the global environment; “eco” being an abbreviation of “ecology”, which also applies in the descriptions below). When the driving is determined to be eco-friendly driving, the in-vehicle display device subtracts the reference value from the travel distance to calculate an eco numerical value indicating the eco-friendly driving in the form of a numerical value and adding up the eco numerical values.
According to another conventional technique, a hybrid vehicle driving operation evaluating device that reports to the driver about the information as to driving operations in actual driving has been suggested. The hybrid vehicle driving operation evaluating device measures ideal fuel consumption data about each driving pattern in a driving test of a hybrid vehicle. Then, the hybrid vehicle driving operation evaluating device measures actual fuel consumption data for each driving pattern in actual driving of the hybrid vehicle, and evaluates the actual driving based on the difference between the ideal fuel consumption data and actual fuel consumption data.
According to yet another conventional technique, a display device that reports to the driver about the driving efficiency of a hybrid electric vehicle and a method of calculating the driving efficiency to be displayed on the display device have been suggested. The display device displays on an eco-meter a correction value that is calculated by correcting the instantaneous fuel consumption calculated based on the travel distance and the amount of fuel consumption of the hybrid electric vehicle, with the acceleration of the hybrid electric vehicle being a parameter.
According to another conventional technique, a fuel consumption display device that can instantly cause the driver to visually recognize the information about the fuel consumption has been suggested. The fuel consumption display device calculates and displays the information about the fuel consumption from the travel distance and the amount of fuel consumption of the vehicle, and changes the luminance and color of a lamp in accordance with the information about the fuel consumption.